Comprehensive Evaluation of Projects with Respect to Sea-Level Change

CESL Benefits and Definitions

Benefits

Benefits of the Comprehensive Evaluation of Projects with Respect to Sea Level Change effort include:

Providing assistance in evaluating robustness of projects to potential Sea Level Change (as part of a nationwide screening and prioritization process to identify projects that need to take Sea Level Change into consideration right away, as well as those that can take longer)

Identification and capture of some of the information about each project that is needed to perform an initial vulnerability assessment and determine if a more detailed project assessment is necessary

Projects determined to be highly susceptible to Sea Level Change will be identified and allow districts to perform more detailed project-scale assessment

Generate custom reports and project specific summaries

Providing to USACE districts and divisions the ability to communicate with other Federal and state agencies as well as local sponsors about projected Sea Level Change impacts

Definitions

Coastal: The term coastal as used in EC 1165-2-212 refers to locations with oceanic astronomical tidal influence, as well as connected waterways with base-level controlled by sea-level. In these latter waterways, influence by wind-driven tides may exceed astronomical tidal influence. Coastal areas include marine, estuarine, and riverine waters and affected lands. (The Great Lakes are not considered "coastal" for the purposes of EC 1165-2-212.).

Datum: A horizontal or vertical reference system for making survey measurements and computations. A set parameters and control points used to accurately define the threedimensional shape of the earth. The datum defines parts of a geographic coordinate system that is the basis for a planar coordinate system. Horizontal datums are typically referred to ellipsoids, the State Plane Coordinate System, or the Universal Transverse Mercator Grid System. Vertical datums are typically referred to the geoid, an Earth model ellipsoid, or a Local Mean Sea Level (LMSL). The current vertical datum used in the United States is the North American Vertical Datum of 1988 (NAVD 88) which replaced the National Geodetic Vertical Datum of 1929 (NGVD 29) (formerly referred to as the Sea Level Datum of 1929).

Eustatic Sea-Level Rise: Eustatic sea-level rise is a change in global average sea level brought about by an increase in the volume of the world ocean [Intergovernmental Panel on Climate Change (IPCC) 2007b].

Global Mean Sea-Level (GMSL) Change: Sea level can change globally due to (i) changes in the shape of the ocean basins, (ii) changes in the total mass of water and (iii) changes in water density. Sea-level changes induced by changes in water density are called steric. Density changes induced by temperature changes only are called thermosteric, while density changes induced by salinity changes are called halosteric (IPCC 2007b).

Local (i.e., "relative") Sea Level: Sea level measured by a tide gauge with respect to the land upon which it is situated. See mean sea level (MSL) and sea-level change (SLC). Relative sealevel change occurs where there is a local change in the level of the ocean relative to the land, which might be due to ocean rise and/or land level subsidence. In areas subject to rapid landlevel uplift, relative sea level can fall (IPCC 2007b). Relative sea level change will also affect the impact of any regional sea level change.

Post-Glacial Rebound: The vertical movement of the land and sea floor following the reduction of the load of an ice mass, for example, since the last glacial maximum (~21,000 years ago). The rebound is an isostatic land movement (IPCC 2007b).

Regional Sea-Level Change: An increase or decrease in the mean level of the ocean's surface over a specific region. Global sea level has regional variations and regional sea-level change may be equal to, greater than, or less than global sea-level change due primarily to regional differences in ocean heating and cooling or to changes in bathymetry. Regional sea-level change as used here does not include local geologic effects, such as subsidence or tectonic movement.

Risk: Risk is a measure of the probability and severity of undesirable consequences (including, but not limited to, loss of life, threat to public safety, environmental and economic damages).

Sea-Level Change: A change in the mean level of the ocean.

Tide Station: A device at a coastal location (and some deep-sea locations) that continuously measures the level of the sea with respect to the adjacent land. Time averaging of the sea level so recorded gives the observed secular changes of the relative sea level (IPCC 2007b).

Tidal Datums: The term tidal datum is used when defined in terms of a certain phase of the tide. Tidal datums are local datums and should not be extended into areas which have differing hydrographic characteristics without substantiating measurements. In order that they may be recovered when needed, such datums are referenced to fixed points known as bench marks.

Uncertainty: Uncertainty is the result of imperfect knowledge concerning the present or future state of a system, event, situation, or (sub) population under consideration. There are two types of uncertainty: aleatory and epistemic. Aleatory uncertainty is the uncertainty attributed to inherent variation which is understood as variability over time and/or space. Epistemic uncertainty is the uncertainty attributed to our lack of knowledge about the system (e.g., what value to use for an input to a model or what model to use). Uncertainty can lead to lack of confidence in predictions, inferences, or conclusions.

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